There has been reports of sysupdater displaying everything installed "succesfully" and get xompletely frozen at "system will reboot in 10 seconds" resulting in a brick for no good reason.
As far as we know this could be a bug in the code just like the first wave of downgrades not being able to do some stuff properly and leaving the 10.3 firm in there and leaving every exploit out there usuless.
So you should be a little more careful when you throw another "as long as you don't do anything stupid with sysUpdater" next time.
I've thought about the Memchunkhax2 for a while and here is my speculation about it.
To get downgrading works, you need the MemchunkHax2, which would involves overwriting KObject and call for free to exploit it, if you don't even know about it as little as I have. At least, every Process running on Kernel would have a KObject (KernelObject). However, the amount of the KObjects would vary, from version to version and from region to region, such as nim is 0x24 for some 8.1J N3DS users, but that's actually 0x25 for me with an O3DS 10.3 (EmuNAND). So if without checking which process this KObject might be for, may cause some issues when you even haven't use that SysUpdater.
NOTE: Even after those are released the KObjects gets a restoration, that is still hard to tell if something important happened for that Processes you picked as victims.
And for Sysupdater. It won't know if the title is preinstalled, or from a newer system version, or from other region. So it would left something weird if you ask me, since the titles that only in newer versions aren't removed. This may cause some problems. Besides, if you're using a modified pack that intended for those guys to update 4.x to it, could cause your MSET and browser be left on a higher version, and invalidate some entrypoints.
Still I would suggest to wait for KTM, and Memchunkhax2 till those are stable enough. Unless you are using a hardmod.
Hope everyone good luck, and the devs have better progress everytime.
@Mrrraou
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before i downgrade , i want to backup my NAND
in 9.2 i can , but in 10.3 it's impossible to use the gateway launcher or even the new GW homebrew
Also for your question. The only way you can dump the first NAND on 9.3+ could be only the hardmod.
Software implemented nand dumping would ask for ARM9 Kernel access.
You may remember what the arm9loaderhax is for, but unfortunately to do that you must set the payload and overwrite the decryption key, thus NAND dump is needed.
Thus making it almost impossible for you to dump it via software, with public known exploits.
Luckily the hardmod isn't that fearsome, you might get someone to do it for you with little fee if you can't do that yourself.
And that benefits the most, cause whenever it bricked due to NAND corrupted, the only way is reflashing a valid dump via hardmod.